This invention relates to clock systems and more particularly to analog clock systems of the type including a master clock or control and a plurality of secondary clocks controlled by the master. Master and slave systems of the analog type were originally impulse type systems in which the secondary clocks were slaves to the master control unit in the sense that they received pulses from the master every minute or other time increment to advance in normal operation. These systems were of pneumatic design including a pressure bellows and interconnecting pneumatic tubing with air pulses being employed to advance the secondary clocks. While these pneumatic type impulse clocks were generally satisfactory, they required considerable maintenance primarily relating to servicing leaks in the system.
In an effort to avoid these maintenance problems, impulse type systems were developed utilizing electric solenoid driven rachet mechanisms. These solenoid systems improve the reliability of the clock systems but have the disadvantage that they are correctable only to the hour so that if the secondary clocks become scattered throughout the system, they have to be manually reset to the proper hour. Solenoid systems with their ratchet mechanisms are also relatively slow and, for example, cannot exceed a pulse rate greater than 60 per minute without risking mechanical failure.
In an effort to overcome the disadvantages of the solenoid type impulse systems, synchronous motor systems were developed in which each secondary clock includes its own synchronous motor driving the clock mechanism so that the secondary clocks operate independently of the master clock and the master clock functions only to provide correction pulses in the event of a power outage or a mechanical failure. These synchronous systems have the advantage that they make available a sweep second hand frequently utilized by the educational market and they make possible the individual correction of secondary clocks more than one hour out of time. However, these synchronous systems, because they require each of the synchronous motors driving the individual synchronous clocks to run continuously, consume a rather large amount of power. They are also relatively complicated in terms of mechanical design, their speed of reset is rather slow, and they are unable to move directly to the correct hour and minute during correction.